;; last edit date: 2016/10/25
;; author: Forec
;; LICENSE
;; Copyright (c) 2015-2017, Forec <forec@bupt.edu.cn>

;; Permission to use, copy, modify, and/or distribute this code for any
;; purpose with or without fee is hereby granted, provided that the above
;; copyright notice and this permission notice appear in all copies.

;; THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
;; WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
;; MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
;; ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
;; WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
;; ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
;; OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.

title forec_t28

.model small
.data
	an dw ?
	bn dw ?
	cn dw ?
	dn dw ?
.code
start:
	mov ax, @data
	mov ds, ax
	mov es, ax
	
	mov ax, an
	mov bx, bn
	mov cx, cn
	cmp ax, 00h
	jz zero
	cmp bx, 00h
	jz zero
	cmp cx, 00h
	jz zero
	mov dx, 00h
	add dx, ax
	add dx, bx
	add dx, cx
	mov dn, dx
	jmp quit
zero:
	mov dn, 00h
quit:	
	mov ah, 4ch
	int 21h
	end start